Python3: Kill main thread when assert on another thread

Question

Please see this code:

#! /usr/bin/env python3

import threading
import time


def asserter():
    time.sleep(3)
    assert False


threading.Thread(target=asserter).start()

while True:
    print('Main')
    time.sleep(1)

I need the main loop to die when the assertion is launched. How should it be done?

Answer 1

You'd need to catch any threaded exceptions in the thread itself. You can then communicate that result back to the main thread somehow. Here's a minimal example that uses a shared flag object to indicate that thread has crashed. The main loop can then simply wait for that flag to change.

import threading
import time

class Flag:
    ended = False

def asserter(flag):
    time.sleep(3)
    try:
        assert False
    except AssertionError:
        flag.ended = True


thread = threading.Thread(target=asserter, args=(Flag,))
thread.start()

while not Flag.ended:
    print('Main')
    time.sleep(1)
print('done')